Niche-Specific Requirement for Hyphal Wall protein 1 in Virulence of Candida albicans

Specialized Candida albicans cell surface proteins called adhesins mediate binding of the fungus to host cells. The mammalian transglutaminase (TG) substrate and adhesin, Hyphal wall protein 1 (Hwp1), is expressed on the hyphal form of C. albicans where it mediates fungal adhesion to epithelial cells. Hwp1 is also required for biofilm formation and mating thus the protein functions in both fungal-host and self-interactions. Hwp1 is required for full virulence of C. albicans in murine models of disseminated candidiasis and of esophageal candidiasis. Previous studies correlated TG activity on the surface of oral epithelial cells, produced by epithelial TG (TG1), with tight binding of C. albicans via Hwp1 to the host cell surfaces. However, the contribution of other Tgs, specifically tissue TG (TG2), to disseminated candidiasis mediated by Hwp1 was not known. A newly created hwp1 null strain in the wild type SC5314 background was as virulent as the parental strain in C57BL/6 mice, and virulence was retained in C57BL/6 mice deleted for Tgm2 (TG2). Further, the hwp1 null strains displayed modestly reduced virulence in BALB/c mice as did strain DD27-U1, an independently created hwp1Δ/Δ in CAI4 corrected for its ura3Δ defect at the URA3 locus. Hwp1 was still needed to produce wild type biofilms, and persist on murine tongues in an oral model of oropharyngeal candidiasis consistent with previous studies by us and others. Finally, lack of Hwp1 affected the translocation of C. albicans from the mouse intestine into the bloodstream of mice. Together, Hwp1 appears to have a minor role in disseminated candidiasis, independent of tissue TG, but a key function in host- and self-association to the surface of oral mucosa.     

Structural insights into thermostable direct hemolysin of Vibrio parahaemolyticus using single-particle cryo-EM

Thermostable direct hemolysin (TDH) is a ~19 kDa, hemolytic pore-forming toxin from the gram-negative marine bacterium Vibrio parahaemolyticus, one of the causative agents of seafood-borne acute gastroenteritis and septicemia. Previous studies have established that TDH exists as a tetrameric assembly in physiological state; however, there is limited knowledge regarding the molecular arrangement of its disordered N-terminal region (NTR)—the absence of which has been shown to compromise TDH's hemolytic and cytotoxic abilities. In our current study, we have employed single-particle cryo-electron microscopy to resolve the solution-state structures of wild-type TDH and a TDH construct with deletion of the NTR (NTD), in order to investigate structural aspects of NTR on the overall tetrameric architecture. We observed that both TDH and NTD electron density maps, resolved at global resolutions of 4.5 and 4.2 Å, respectively, showed good correlation in their respective oligomeric architecture. Additionally, we were able to locate extra densities near the pore opening of TDH which might correspond to the disordered NTR. Surprisingly, under cryogenic conditions, we were also able to observe novel supramolecular assemblies of TDH tetramers, which we were able to resolve to 4.3 Å. We further investigated the tetrameric and inter-tetrameric interaction interfaces to elaborate upon the key residues involved in both TDH tetramers and TDH super assemblies. Our current structural study will aid in understanding the mechanistic aspects of this pore-forming toxin and the role of its disordered NTR in membrane interaction.     

A hepatic membrane-associated factor stimulates nuclear DNA synthesis in cultured fibroblastic cells

Nuclear DNA replication in cultured mouse fibroblasts is stimulated by isolated hepatic plasma membranes in a time- and concentration-dependent manner. The plasmalemmal activity is susceptible to trypsin treatment, and to treatment with protein modifying agents, N-ethylmaleimide, N-bromosuccinimide, and 2-hydroxy-5-nitro-benzylbromide.     

p53 Represses the Mevalonate Pathway to Mediate Tumor Suppression

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Glycosylation-induced conformational modification positively regulates receptor-receptor association: a study with an aberrant epidermal growth factor receptor (EGFRvIII/DeltaEGFR) expressed in cancer cells

The epidermal growth factor receptor (EGFR) is a multisited and multifunctional transmembrane glycoprotein with intrinsic tyrosine kinase activity. Upon ligand binding, the monomeric receptor undergoes dimerization resulting in kinase activation. The consequences of kinase stimulation are the phosphorylation of its own tyrosine residues (autophosphorylation) followed by association with and activation of signal transducers. Deregulation of signaling resulting from aberrant expression of the EGFR has been implicated in a number of neoplasms including breast, brain, and skin tumors. A mutant epidermal growth factor (EGF) receptor missing 267 amino acids from the exoplasmic domain is common in human glioblastomas. The truncated receptor (EGFRvIII/DeltaEGFR) lacks EGF binding activity; however, the kinase is constitutively active, and cells expressing the receptor are tumorigenic. Our studies revealed that the high kinase activity of the DeltaEGFR is due to self-dimerization, and contrary to earlier reports, the kinase activity per molecule of the dimeric DeltaEGFR is comparable to that of the EGF-stimulated wild-type receptor. Furthermore, the phosphorylation patterns of both receptors are similar as determined by interaction with a conformation-specific antibody and by phosphopeptide analysis. This eliminates the possibility that the defective down-regulation of the DeltaEGFR is due to its altered phosphorylation pattern as has been suggested previously. Interestingly, the receptor-receptor self-association is highly dependent on a conformation induced by N-linked glycosylation. We have identified four potential sites that might participate in self-dimerization; these sites are located in a domain that plays an important role in EGFR functioning.     

Intensive statin therapy in acute coronary syndromes: clinical benefits and vascular biology

PURPOSE OF REVIEW: The results of a landmark clinical study comparing intensive statin therapy with conventional statin therapy, in patients with acute coronary syndromes (ACS), are reviewed. The mechanisms behind these results are analysed drawing data from vascular and cell biology. RECENT FINDINGS: The Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis in Myocardial Infarction (PROVE IT-TIMI 22) study showed that intensive statin therapy with 80 mg of atorvastatin to achieve a low-density lipoprotein cholesterol of 62 mg/dl resulted in a 3.9% absolute and a 16% relative risk reduction in death or major cardiovascular events up to 2 years, compared to 40 mg of pravastatin, in patients with ACS. The results were especially significant as intensive statin therapy resulted in a very early benefit (<30 days) and occurred against a background of percutaneous coronary intervention (69%) for the index admission and high use of medications for secondary prevention. The PROVE IT and the Myocardial Ischaemia Reduction with Aggressive Cholesterol Lowering (MIRACL) C-reactive protein sub-study also showed that atorvastatin (80 mg) resulted in a significant reduction in markers of inflammation, whilst the Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) study showed that intensive statin therapy was associated with reduced progression of atherosclerosis compared with conventional doses of statins. SUMMARY: Intensive statin therapy results in a significant early reduction in adverse cardiac events in ACS patients which are sustained over 2 years. The early benefits seen are likely to result from modulation of inflammation, endothelial function and coagulation, i.e. the pleiotropic effects, whereas the greater reduction in low-density lipoprotein cholesterol results in reduced long-term events.     

A neuronal isoform of CPEB regulates local protein synthesis and stabilizes synapse-specific long-term facilitation in aplysia

Synapse-specific facilitation requires rapamycin-dependent local protein synthesis at the activated synapse. In Aplysia, rapamycin-dependent local protein synthesis serves two functions: (1) it provides a component of the mark at the activated synapse and thereby confers synapse specificity and (2) it stabilizes the synaptic growth associated with long-term facilitation. Here we report that a neuron-specific isoform of cytoplasmic polyadenylation element binding protein (CPEB) regulates this synaptic protein synthesis in an activity-dependent manner. Aplysia CPEB protein is upregulated locally at activated synapses, and it is needed not for the initiation but for the stable maintenance of long-term facilitation. We suggest that Aplysia CPEB is one of the stabilizing components of the synaptic mark.     

Phenotyping Mouse Pulmonary Function In Vivo with the Lung Diffusing Capacity

The mouse is now the primary animal used to model a variety of lung diseases. To study the mechanisms that underlie such pathologies, phenotypic methods are needed that can quantify the pathologic changes. Furthermore, to provide translational relevance to the mouse models, such measurements should be tests that can easily be done in both humans and mice. Unfortunately, in the present literature few phenotypic measurements of lung function have direct application to humans. One exception is the diffusing capacity for carbon monoxide, which is a measurement that is routinely done in humans. In the present report, we describe a means to quickly and simply measure this diffusing capacity in mice. The procedure involves brief lung inflation with tracer gases in an anesthetized mouse, followed by a 1 min gas analysis time. We have tested the ability of this method to detect several lung pathologies, including emphysema, fibrosis, acute lung injury, and influenza and fungal lung infections, as well as monitoring lung maturation in young pups. Results show significant decreases in all the lung pathologies, as well as an increase in the diffusing capacity with lung maturation. This measurement of lung diffusing capacity thus provides a pulmonary function test that has broad application with its ability to detect phenotypic structural changes with most of the existing pathologic lung models.     

Galactan sulfate of Grateloupia indica: Isolation, structural features and antiviral activity

Natural compounds offer interesting pharmacological perspectives for antiviral drug development with regard to broad-spectrum antiviral properties and novel modes of action. In this study, we have analyzed polysaccharide fractions isolated from Grateloupia indica. The crude water extract (GiWE) as well as one fraction (F3) obtained by anion exchange chromatography had potent anti-HSV activity. Their inhibitory concentration 50% (IC₅₀) values (0.12-1.06 μg/ml) were much lower than cytotoxic concentration 50% values (>850 μg/ml). These fractions, which were effective antiviral inhibitors if added only during the adsorption period, had very low anticoagulant activity. Furthermore, they had no direct inactivating effect on virions in a virucidal assay. Chemical, chromatographic and spectroscopic methods showed that the active polysaccharide, which has an apparent molecular mass of 60 kDa and negative specific rotation −16° (c 0.2, H₂O), contains α-(1 → 4)- and α-(1 → 3)-linked galactopyranose residues. Sulfate groups, if present, are located mostly at C-2/6 of (1 → 4)- and C-4/6 of (1 → 3)-linked galactopyranosyl units, and are essential for the anti herpetic activity of this polymer.